Exam 2 (Ch. 6 Microbial Growth) Flashcards Preview

Growth (def.)

increase in number of cells

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colonies

groups of cells that can be seen without a microscope

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what does CFU stand for

colony forming units

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another name for colony forming units is

colony

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things needed for growing microbes (4 things)

1. chemical needs for microbe must be determined-media (what do they eat)2. media is made and sterilized (autoclaved)3. microbe is inoculated into media4. inoculated media is placed in proper env't (temp, pH, oxygen, light, etc.)

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autoclave (def.)

heat under pressure for 20 min.

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culture (def.)

microbe growing on the media

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inoculate (def.)

process of adding/ introducing microbes to the media

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incubate (def.)

the appropriate time and temp to grow the specific bacteria

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enrichment culture (def.)

set of conditions such as temp, pH, salinity, light, nutrients, and oxygen that are tailored to requirements of desired microbe

likes to live in your stomach and can cause ulcers

alkaliphiles (3 things)

1. opt. pH above 82. found in soda lakes3. ex: Bacillus alkalophilus

neutrophiles (2 things)

1. opt. pH 72. most bacteria are in this category

halophiles (3 things)

1. require high salt concentration2. found in Dead Sea or Great Salt Lake3. ex: Halococcus

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growth requirements for most microbes (3 things)

1. mesophiles2. pH (neutral) 73. little salt

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plate count (2 things)

1. most common method2. measures number of viable cells

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serial dilution (explain)

bacteria are added to tubes at varying dilutions, poured into plates, allowed to grow

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a plate with the highest dilution will have the _______ amount of bacteria (growth)

least

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pour plate method (5 things)

1. bacteria added to liquid agar2. mixture poured into empty plates3. agar solidifies, plate incubated4. colonies grow within and on surface of agar5. plates with 30-300 colonies are used to calculate original cell concentration

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spread plate method (3 things)

1. bacteria added to solid agar2. spread over surface of agar with sterile rod3. colonies only on surface of agar

pour plate and spread plate

4 types of measurement for microbial growth

MPN stands for

most probable number

turbidity (4 things)

1. more bacteria in liquid culture means more turbid (cloudy)2. beam of light passes through the test tube3. more bacteria, less light will pass through4. uses spectrophotometer

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most probable number (MPN) (5 things)

1. used when plate counts aren't reliable2. estimates number of microbes in original sample using a serial dilution3. positive results seen by gas production4. a table estimates the number of microbes in original sample 5. used in testing water purity

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generation

1 cell dividing into 2

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generation time

time it takes for the population size to double

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growth curve (3 things)

1. graph that plots growth of a population 2. used to calculate generation time3. uses logarithmic scale

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4 phases of growth, in order

lag phase, log or exponential phase, stationary phase, death phase

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lag phase (2 things)

1. period of adjustment2. slow growth

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log or exponential phase

population is doubling

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stationary phase (2 things)

1. equal number of cells dividing and dying2. due to depletion of nutrients, accumulation of waste, drop in pH

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death phase

cells are dying

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2 ways of preserving bacterial cultures

flash-freezing and lyophilization

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flash-freezing

pure culture of bacteria are quickly frozen at -50 to -95 degrees Celsius

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lyophilization (4 things)

1. pure culture is flash frozen2. vacuum is used to remove water3. result is powder residue4. bacteria revived by adding liquid media